BACKGROUND AND OBJECTIVES: Fluorescence-guided resection (FGR) of malignant gliomas with five-aminolevulinic acid (5-ALA) is an established method using surgical microscopes equipped with filter systems for observing fluorescence. Over the past decade, new technologies have been introduced for the same purpose, with available publications evaluating their clinical efficacy based on varying criteria. This study aims to review technologies and concepts of validation in the context of 5-ALA–mediated FGR. METHODS: A systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement was performed to identify devices capable of detecting 5-ALA–induced fluorescence. Articles found eligible for this review were analyzed, focusing on the methods of validation used for novel devices. A qualitative analysis is presented. RESULTS: Using predefined eligibility criteria, 22 studies were analyzed. Publications on the following visualization devices were reviewed: FL400 (Leica Microsystems), Aeos (Aesculap), BLUE400 and BLUE400 AR Filter System (Carl Zeiss Meditec AG), Endoscope with D-Light C (Karl Storz), Fiberscope N-4L (Machida), ORBEYE 4K 3D Digital Video Microscope (Olympus), and several customized surgical loupe systems. In many cases, validation seemed unstandardized, with inherent biases and limited reproducibility. CONCLUSION: This review illustrates the significance of device validation within the framework of FGR. It emphasizes the criticality of validating devices in accordance with established standard, i.e. the BLUE400 filter system, which was employed in the approval studies of 5-ALA. Furthermore, standardized concepts of validation are required to assess whether new devices are, in fact, a reliable or superior alternative in the field of FGR. Published guidelines should be considered when performing future studies.